Electronic technology is a field that has shown remarkable advances in the recent past. One of the significant innovations in the field has been the printed circuit board. With this innovation, even very complex circuitry can be reduced from a bulky mass to an easy-to-handle planar unit known as a printed circuit board. The boards eliminate the requirements for bulky wiring and provide consistent spatially compact structures for handling complex tasks. The boards can simply be "plugged" into electronic systems, greatly facilitating the design, manufacture, and repair of electronic equipment. For repair functions, the modular aspects of the boards greatly simplify the repair process. New boards can simply be plugged in the place of the malfunctioning units and the old defective elements can be repaired off line with little down time to the function of the equipment.
A byproduct of the "plug-in," modular, aspect of the circuit boards is that it becomes necessary to maintain an inventory of boards on hand. A minimum requirement would be two or more of each type of board utilized in repair and maintenance operations. In an operation of any complexity, storage of the boards can become a problem.
Storage is a problem common to many business environments. Not only storage of materials, such as circuit boards, but also of peripheral items, such as paperwork. One aspect common to nearly all business situations is that storage space is expensive; hence myriad systems have been designed with the goal of higher density storage in mind.
Two such systems of interest are the hanging filing device disclosed in U.S. Pat. No. 2,223,978, issued to Marcus C. Dew, and the friction type binder disclosed in U.S. Pat. No. 2,869,210, issued to Oscar Kain Schneider. These two systems both show methods of storage by vertical suspension. The Dew device uses clips suspended from a rod to support the stored items. The Schneider system uses a pair of support rods on a rack to suspend the stored product.
There are also inventions dealing directly with the storage of printed circuit boards, two of which are U.S. Pat. Nos. 4,382,517, issued to John H. Welsch, and U.S. Pat. No. 4,385,781, issued to John H. Welsch and Robert J. Carver. Both of these devices allow high density storage of circuit boards of a given size.
These prior art devices all have shortcomings when applied to storage of circuit boards of varying sizes. The Dew and Schneider disclosures both relate to storage of paper products. The clamping and storage mechanisms were designed with that in mind. No electrical aspects were considered, and hence there is no provision for protection from static charge accumulation. There is also no provision for the increased weight and fragility factors present with circuit board applications.
Also, since the Dew and Schneider inventions were intended for the storage of files of greatly varying thicknesses, the clamping devices are spring-loaded. This creates a more complex mechanism than is necessary for storage of items of uniform, or nearly uniform, thickness.
The main disadvantage of the Welsch inventions, at least for the presently desired applications, is that there is no adequate provision made for variation in the dimensions of length and width. These are dimensions that will significantly differ among various printed circuit boards adapted for varying purposes. The Welsch devices consider the uniform thickness of the boards, but require adjustment for length variation. This, of course, rules out the possibility of the storage of different sized boards in a single device.
None of the prior art storage devices provide the flexibility necessary to store circuit boards of varying length and width. The prior art also makes no specific provision for protection from static charge buildup.